The role of SRF in the decarbonization of the cement industry 

The cement industry faces one of its greatest historical challenges: decarbonizing its processes without compromising competitiveness or energy supply security. One of the most effective strategies to move toward this goal is replacing fossil fuels with more sustainable alternatives. In this context, the use of solid recovered fuel (SRF) presents an excellent opportunity to recover energy from non-hazardous waste and reduce cement’s carbon footprint. 

In the province of Barcelona, the Pronatur project stands out as a pioneering example of how this circular economy approach can be implemented. This vertically integrated initiative, led by Molins, was designed to ensure a continuous, high-quality supply of SRF to our Sant Vicenç dels Horts plant. Since its launch in 2011, the Pronatur facility has transformed the management of non-hazardous industrial and commercial waste—waste that would otherwise have ended up in authorized landfills—turning it into a high-performance energy resource for Molins’ cement plant. 

The challenge Pronatur addresses is twofold. On one hand, it helps solve the problem of valorizing waste that has historically been dumped in landfills, generating emissions and occupying increasingly scarce space. On the other, it provides a real, local alternative to petroleum coke (petcoke), a fossil fuel that is not only imported but also has a higher CO₂ emission factor. Replacing petcoke with this alternative fuel not only reduces external energy dependence but also lowers total emissions from the cement production process, in line with the company’s decarbonization commitment. 

From industrial waste to a local alternative fuel 

The location of Pronatur in Montornès del Vallès, about 35 kilometers from the Sant Vicenç dels Horts cement plant, is key to its efficient and sustainable supply model. The facility was designed to operate under a just-in-time model, minimizing storage needs and ensuring a constant, stable flow of high-quality fuel. 

Since its launch, the Pronatur treatment plant has recovered over 680,000 tons of non-hazardous industrial and commercial waste. These materials—paper, cardboard, non-PVC plastics, wood, textiles, and rubber—are carefully sorted and processed to meet strict technical standards. These specifications ensure a homogeneous, efficient fuel that is compatible with the Sant Vicenç dels Horts cement kiln, in full compliance with current European regulations. 

The industrial process that transforms these heterogeneous wastes into a high-quality fuel is highly specialized. It begins with primary shredding, which reduces material size and allows for more efficient separation. Next comes the removal of ferrous metals using magnets, screening to adjust particle size, and density separation to differentiate materials based on specific weight. A crucial step is the optical separation of PVC, performed with NIR (near-infrared) technology, which precisely identifies PVC plastics for removal. Finally, the material undergoes secondary shredding to reach the desired particle size before being transported to the shipping and storage section. 

In recent years, the plant has invested in enhancing its capacity and flexibility. Since last year, Pronatur has operated an additional line to produce fine SRF with improved quality compared to conventional coarse SRF, intended for the cement kiln’s main burner. This allows the plant to respond more quickly to production needs and increase the thermal substitution rate, further reducing the consumption of fossil fuels. 

Moreover, one of Pronatur’s distinguishing features is its commitment to advanced quality control technology. The facility is equipped with NIR optical separators specialized in identifying and removing PVC, as well as an online analyzer that measures critical parameters in real time, such as calorific value, chlorine content, and moisture. This system provides continuous process data, enabling immediate adjustments to ensure the final product meets strict quality standards. The result is a reliable, consistently specified alternative solid fuel, optimized for energy recovery in cement production. 

Continuous industrial operation and commitment to sustainability 

The plant operates continuously with rotating shifts, staffed by qualified personnel experienced in SRF production, ensuring the supply of alternative fuel to the cement plant seven days a week. This setup allows for a steady flow, coordinated with the demand of the Sant Vicenç dels Horts plant, maximizing both logistical and energy efficiency. 

Pronatur’s sustainability model goes beyond fossil fuel savings and direct CO₂ emission reductions. It also has a significant impact on reducing landfill waste, preventing tens of thousands of tons of non-hazardous materials from being disposed of each year. This is a local, replicable solution that lowers the environmental footprint and promotes a circular economy model based on resource recovery. 

Another key aspect of Pronatur’s approach is its commitment to innovation in safety and training. This year, the plant has implemented a virtual reality training system for fire drills, available both with VR headsets and on specialized PCs. This system allows plant staff—especially new employees—to practice using fire detection and suppression systems without interrupting production or creating real risks. 

A circularity model 

The result of this integration is a robust model that not only ensures a continuous, local supply of alternative fuel but also generates environmental, social, and economic value. Thanks to this strategy, the Sant Vicenç dels Horts cement plant can gradually replace petcoke with SRF, reducing its carbon footprint and enhancing long-term sustainability. 

The Pronatur project demonstrates that energy recovery from non-hazardous waste is not just a theoretical possibility, but a mature and viable solution for the cement industry. It is a success story in circular economy, where waste that was once a problem becomes a local resource—cutting emissions, creating jobs, and strengthening energy independence. With ongoing investments in technology, quality control, and training, the Montornès del Vallès plant consolidates a model that serves as a benchmark for advancing a more sustainable and competitive construction sector. 

Published in International Cement Review